Changed the upload-pages-artifact version from the supposedly correct v4 to the allegedly already deprecated v3

Author: Philip-Schaer

.github/workflows/jekyll-gh-pages.yml

@@ -36,7 +36,7 @@ jobs:
           source: ./
           destination: ./_site
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v4
+        uses: actions/upload-pages-artifact@v3
 
   # Deployment job
   deploy: